Malt beverages, such as beer, contain small quantities of proteinaceous material and tannins which can react to form a precipitate that renders the beer hazy or cloudy. To prevent the formation of this haze or precipitate, adsorbant materials, commonly referred to as chill stabilizing agents, have been added to the beer prior to filtering to remove the tannins and/or proteinaceous material and thereby prevent the formation of the haze. Polyvinylpolypyrrolidone (PVPP) has been used in the past as an adsorbant for tannins, while silica gel has seen extensive use as an adsorbant for the proteinaceous materials.
In the traditional practice, the adsorbant is added to the beer as a slurry and is removed during filtration as part of the filter heel, which is a mixture of the adsorbant particles containing the adsorbed material, as well as filter aid particles, such as diatamaceous earth. Because of the mixture of materials in the filter heel, it has not been practical to recover the adsorbant for reuse.
As polyvinylpolypyrrolidone is a relatively expensive material, attempts have been made in the past to use PVPP in the filter in the form of sheets which can be regenerated. While the sheets are capable of being removed and regenerated for reuse, the sheets, during use, become progressively contaminated with the adsorbed material, so that the PVPP loses its efficiency, with the result that the removal of tannins is not uniform and consistent.